According to very good sources, the latest version of Mac OS X has a couple of very interesting file system features worth knowing about:
- Automatic File Defragmentation: When a file is opened, if it is highly fragmented (8+ fragments) and under 20MB in size, it is defragmented. This works by just moving the file to a new, arbitrary, location on the disk, though this only happens on Journaled HFS+ volumes. [ref]
- Adaptive Hot File Clustering: Over a period of days, the OS keeps track of files that are read frequently – these are static files under 10MB. At the end of each tracking cycle, the “hottest” files (the files that have been read the most times) are moved to a “hotband” on the disk – a part of the disk that’s particularly fast given the physical disk characteristics (currently sized at 5MB per GB). “Cold” files are evicted to make room. As a side effect of being moved into the hotband, files are defragmented. Currently, AHFC only works on the boot volume, and only for Journaled HFS+ volumes over 10GB. [ref]
Cool stuff, eh? Another great reason to get your hands on Panther.
